Occurs in reefs, mangroves, and marine lakes. Predominantly in shallow areas. Notably, a large population inhabit the marine lake of Tanah Bambam, where C. porosa was the dominant representative of moon sponges. This species produces 1-2 mm sized buds (Figure 8) and buds extensively in marine lakes habitats.

Distribution.

According to the material examined in this revision, we observed that this species is widely distributed in the Indo-Pacific, from the Chagos archipelago, Sri Lanka, Australia, and Tonga Islands. In Indonesia, C. porosa has been collected in East Kalimantan, Java, Ternate, and West Papua.

Remarks.

Cinachyrella porosa is distinguished from C. australiensis by the absence of acanthose microxea and smaller size of sigmaspires. The first species described with these two diagnostic characteristics was Spiretta porosa Lendenfeld, 1888, subsequently transferred to the genus Tetilla ( Lendenfeld 1903) and included as a junior synonym of C. australiensis in both, Burton (1934) and WPD (2018). The detailed examination of the holotype of C. porosa suggests that this species should therefore be resurrected. Based on the careful examination of the holotypes of C. albabidens (Lendenfeld, 1907) and C. albaobtusa (Lendenfeld, 1907), and the descriptions and plates of C. malaccensis (Sollas, 1902) and C. clavigera (Hentschel, 1912), we coincide with the porosa -group recognized by Burton (1934). However, we disagree with the statement that intermediate forms can be found within the wide range of variation of C. australiensis, and therefore we consider C. porosa as a valid species clearly differentiated from C. australiensis. Lendenfeld (1907) recognized the difficulties to separate the three species of the alba -group, and his decision to discriminate them as different species was based on distant localities and slight differences on the abundance of triaenes. After the morphological analysis of the C. albatridens holotype, we consider that this species could also be a junior synonym of C. porosa because neither microxea nor other characters to separate this species were found. Although Burton (1934) did not consider C. anomala (Dendy, 1905) within the porosa -group, we suggest that a similar decision could be made based on our observations of the type specimen. Some of the Indonesian specimens have silica micro-spherules. Similar spherules have been described for species C. anomala and C. hirsuta (Dendy, 1905), as well as Tetilla cinachyroides ( Hentschel 1911). Because C. hirsuta and T. cinachyroides contain acanthose microxea, they are synonimized with C. australiensis. The nature of these spherules has been discussed by Dendy (1905) and Lendenfeld (1907). Dendy (1905) suggests that the spherules are associated with mother cells, which probably would give origin to sigmaspires, or they can be considered as anomalous or incidental spicules. On the other hand, Lendenfeld (1907) estimated that spherules are the earlier stages of oxeas as described for Tethya cranium (see Lendenfeld 1907, plate 14 figs 11-15). Silica spherules are very variable within populations of the same species and among different genera in Tetillidae, suggesting that this character has no taxonomic value.